update version-check message in setup.py and IPython.__init__

clearer message that IPython no longer supports 2.6.

IPython/__init__.py

@@ -28,8 +28,8 @@
 #-----------------------------------------------------------------------------
 
 # Don't forget to also update setup.py when this changes!
-if sys.version[0:3] < '2.6':
-    raise ImportError('Python Version 2.6 or above is required for IPython.')
+if sys.version_info[:2] < (2,7):
+    raise ImportError('IPython requires Python Version 2.7 or above.')
 
 # Make it easy to import extensions - they are always directly on pythonpath.
 # Therefore, non-IPython modules can be added to extensions directory.

setup.py

@@ -26,12 +26,10 @@
 
 # This check is also made in IPython/__init__, don't forget to update both when
 # changing Python version requirements.
-#~ if sys.version[0:3] < '2.6':
-    #~ error = """\
-#~ ERROR: 'IPython requires Python Version 2.6 or above.'
-#~ Exiting."""
-    #~ print >> sys.stderr, error
-    #~ sys.exit(1)
+if sys.version_info[:2] < (2,7):
+    error = "ERROR: IPython requires Python Version 2.7 or above."
+    print(error, file=sys.stderr)
+    sys.exit(1)
 
 PY3 = (sys.version_info[0] >= 3)